1. Given the following two perfectly legal C++ declarations

   class point {
     
       point(double X, double Y, double Z) {
         // whatever
         }
   
     private:
   
       double normalize(double x, double y) {
         // whatever
         }
   
       double x, y, z;
     };
   
   
   struct line {
     point end_point1, end_point2;
     };
   

   indicate whether each of the following statements are legal C++ or not, and explain why:

   1	point pt1;
   2	point pt2(1.0, 2.0, 3.0);
   3	line ln1;
   4	cout << "x = " << ln1.end_point1.x << endl;

   ---

   point pt1; - Not legal; this declaration uses the default constructor (the constructor with no parameters), which is not defined for point.

   point pt2(1.0, 2.0, 3.0); - Not legal; this declaration uses the constructor point(int, int, int), which exists but has the default class access permission private and so is unaccessible outside the class point.

   line ln1; - This one I screwed up. This is illegal because line doesn't have a default constructor. When I first wrote the quiz, this was legal because the class point had a default constructor.

   cout << "x = " << ln1.end_point1.x << endl;' - This is illegal because x is a private member variable in class point and cannot be accessed outside a point. The access privilege applied to an instance of a class has no effect on the access privileges applied to the members of the class.

   ---

2. Write the code for the function having the prototype

   void uppercase_b(char str[]);
   

   that accepts as input the null-byte terminated array of characters str and changes every lower-case b into an upper case B only if the b is preceded by a (in either case) and followed by c (in either case). For example, abC should be changed to aBC but cba should remain unchanged.

   ---

   void uppercase_b(char str[]) {
   
     if (str[0] == '\0') return;
   
     for (int i = 1; str[i] != '\0'; i++)
       if ((tolower(str[i - 1]) == 'a') &&
           (str[i] == 'b') &&
           (tolower(str[i + 1]) == 'c')) str[i] = 'B';
     }
   

   ---

3. A colleague of yours wrote the following program

   #include <iostream>
   
   static void set_to_five(int x) {
     x = 5;
     }
   
   int main() {
     int i;
     set_to_five(i);
     cout << "i = " << i << endl;
     }
   

   Your colleague was puzzled when the program successfully compiled and ran, but produced the following output:

   i = -4264572
   

   Recognizing your expertise as a C++ programmer, your colleague comes to you for an explanation. What do you say?

   ---

   Your colleague's problems apparently stems from the belief that changing a parameter inside a function will case the change to appear outside the function too. Only array parameters allow changes made inside a function to appear outside the function.

   ---

This page last modified on 3 July 2001.